There exist various methods for producing non-wovens. When forming spun-bonded fabrics by means of spun-bonding or melt-blowing methods, the filaments formed from extruded polymers by melt-spinning are pressed through spinnerets under high pressure, stretched in a hot or cold air stream and piled into a non-woven. The non-woven can then be bonded chemically, mechanically or thermally. When producing airlaid non-wovens, staple fibers are used, which are first carded to form a fibrous web and then bonded chemically, mechanically or thermally.
In particular, hydrophilic non-wovens are used as covering non-wovens or as an intermediate non-woven for sanitary products such as diapers, sanitary towels, incontinence products and similar products. The function of such non-wovens is to quickly transfer body fluids such as urine and blood to the underlying absorption layer.
To produce hydrophilic non-wovens, mostly fibers or filaments made of thermoplastic polymers such as polyolefin or polyester are used. However, these polymers are hydrophobic and have thus to be provided with a hydrophilic finish either during fiber production and/or during further processing into a non-woven. Usually, hydrophilization is performed by treating the filaments with known spin finishings, and the filaments are then further processed into staple fibers and/or directly into non-wovens. Further, it is also common to treat the non-wovens with a hydrophilic finishing agent to form a so-called top coat prior to further processing them into a sanitary product.
The treatment of hydrophobic fibers, filaments or non-wovens with a hydrophilic spin finish or a hydrophilic finishing agent is to result in a hydrophilicity that is as permanent and constant as possible over a long period of useful life of the non-woven. Therefore, the hydrophilic spin finish or the finishing agent should well adhere to the hydrophobic non-woven and must not or only minimally be washed off by liquids. Modern non-wovens should exhibit permanent hydrophilicity and be capable of being repeatedly wetted with water or body fluids such as urine.
So far, the compositions for the hydrophilic finishing of non-wovens and fibers for sanitary applications have been sold either as almost water-free oils or as diluted aqueous dispersions to achieve a permanent hydrophilization of the fibers or non-wovens. The commercially available compositions are then diluted with water on-site during the production of the fibers or non-wovens, applied onto the fibers or non-wovens from the aqueous dilution and then dried.
However, the commercially available oils do not lead to a satisfactory permanent hydrophilic finish. The products provided with such a finish often show insufficient results in the wash-off test and have a tendency towards wet migration. Although the aqueous dispersions show better results regarding the permanent hydrophilic finishing of textile fibers and non-wovens, the high water content of these dispersions can lead to bacterial contamination or hydrolysis of the components used and thus to a limited storage stability.
The patent DE 196 45 380 B4 discloses a composition for permanent hydrophilization of polyolefin fibers comprising cationically modified siloxanes, esterquats and non-ionic surfactants. However, all commercially available compositions contain water and/or solvents and have only limited storage stability.